The scandium doped Aluminum nitride alloy (ScAlN) thin films were prepared using DC reactive magnetron sputtering method with a scandium aluminum alloy target on n type silicon substrates at different substrate temperatures. The influence of substrate temperature on the crystalline structure, the surface morphology and the resistivity of ScAlN thin films was investigated by XRD, AFM and a standard I V module of the ferroelectric test system. It was statistically proved that the (002) oriented peak intensity of ScAlN thin film first increased and then decreased, reaching the best crystalline state at 650 ℃. The RMS value of films decreased with the temperature increasing, reaching 3.064 nm and 2.804 nm respectively at 650 ℃ and 700 ℃. The film surface was cracked locally when temperature was up to 700 ℃. So, 650 ℃ was regarded as the most proper temperature. The resistivity of ScAlN film first increased and then decreased with the temperature increasing.